A. Technical Field
The present invention relates to a sensor controller, and more particularly, to a controller having a closed loop to control the oscillation amplitude of a resonating mass in a sensor.
B. Background of the Invention
A rate of rotation sensor has been widely applied to measure the angular velocity of a moving object. FIG. 1 shows a schematic diagram 100 of a conventional gyroscope for measuring the rate of rotation of a sensor. As depicted, the conventional gyroscope includes: a sensor signal processor 114 for processing a sensor signal 106 from the sensor of a sensor unit 102; and a driver signal processor 112 for generating and providing a driver signal (or, equivalently, forcing signal or excitation signal) 108 to a driver of the sensor unit 102.
Such a conventional system has several problems. First, the excitation frequency, which is derived from the system clock, may not be close to the resonant frequency under certain circumstances, such as the start-up stage or transient stages caused by an external shock event. An error of a few percent in the system clock frequency, which is typically an integer multiple of the resonant frequency in the steady state only, from its target frequency can generate a very long start-up time or even make it impossible to start the sensor movement. As a consequence, the conventional system requires a factory calibration of the voltage-controlled oscillator (VCO) of the system clock.
Second, a conventional system is implemented mostly in analog domain, i.e., it uses more analog components than digital components. Since a large portion of the processes in the controller are based on analog functions, the conventional controller has low immunity to process spread, while it typically has a high form factor and a high power consumption rate.
Therefore, a better solution is needed to address the main issues, including long start-up time, low immunity to process spread, poor protection against external shock events, large form factor, and low efficiency in power consumption, of the conventional sensor controller.